I might regret saying it, but I think we as humanity should go back to wars being definitively won, rather than dragging on indefinitely. It's obviously a poor metaphor, but I'm thinking of something like the "Fifty-move rule" in chess - e.g. if no significant area changed sides in e.g. 100 days, then we officially redraw the maps (by treaty if possible), cease hostilities and let people rebuild and get on with their lives.
Geneva conventions don't really have a good enforcement story, either - not against countries like Russia (or China, or US). If you're Rwanda or Yugoslavia, that's a different story, but note that in those cases it was UNSC that established the corresponding tribunals, so if the violator has UNSC veto power, that avenue is effectively blocked.
> A Pan Am 727 flight, waiting for start clearance in Munich, overheard the following:
> Lufthansa (in German): "Ground, what is our start clearance time?"
> Ground (in English): "If you want an answer you must speak in English."
> Lufthansa (in English): "I am a German, flying a German airplane, in Germany. Why must I speak English?"
> Unknown voice from another plane (in a beautiful British accent): "Because you lost the bloody war"